Abstract
BACKGROUND: Although the safety of the BBIBP-CorV (Sinopharm) vaccine has been confirmed in both adults and children, safety data remain limited for individuals under 18 years of age. This longitudinal study in Iran aimed to investigate reactogenicity, breakthrough infections, and serious adverse events following Sinopharm vaccination in this population. METHODS: In this cohort event monitoring study, children and adolescents aged 5 to 18 Years in the eight cities around the country were invited to participate after receiving the first dose of the vaccine. The assessment of local and systemic reactogenicities was conducted through daily telephone calls for up to seven days following the first and second doses of the vaccine. Severe adverse events, adverse events of special interest (AESI), and COVID-19 infections were monitored with weekly follow-ups. Follow-up lasted for 13 weeks for those who received one dose of the vaccine and 17 weeks for those who received two doses. Adverse events were reported as percentages along with 95% confidence intervals (CI). The total person-time at risk was used to calculate the incidence rate of COVID-19 infections, and factors associated with COVID-19 were analyzed using Cox survival analysis. RESULTS: Among the 18,528 participants (50.5% female), the mean age was 11.9 ± 3.4 years (age range: 4.6-18.6). Only 57.4% of participants received the second dose of the vaccine. The incidence rate of COVID-19 infection was 28.9 (95% CI: 26.4-31.6) per 100,000 person-days. Two cases were classified as AESI: one case of generalized convulsion and one case of diabetic ketoacidosis. Reactogenicity was investigated in a subset of 945 participants, 184 of whom received the second vaccine dose. The most frequent local and systemic reactogenicity events on the first day after vaccination were as follows: pain at the injection site-26.7% (95% CI: 23.5-29.8) after the first dose and 53.3% (95% CI: 46.0-60.5) after the second dose; headache-6.0% (95% CI: 4.4-7.7) after the first dose and 8.7% (95% CI: 4.6-12.8) after the second dose; fatigue-3.7% (95% CI: 2.3-5.0) after the first dose and 7.1% (95% CI: 3.4-10.8) after the second dose; and malaise-2.9% (95% CI: 1.7-4.1) after the first dose and 7.6% (95% CI: 3.8-11.5) after the second dose. Most reactogenicity events subsided gradually and did not interfere with the participants' daily activities. CONCLUSIONS: Sinopharm is a safe and well-tolerated vaccine option for children and adolescents and can be recommended for this population.